The Linux Programming Interface

614 Chapter 28

Timers

Interval timers Yes No setitimer().

Timers set by alarm() Yes No alarm().

POSIX timers No No timer_create() and related calls.

POSIX threads

Threads No See

notes

During fork(), only calling thread is replicated in

child.

Thread cancelability state

and type

No Yes After an exec(), the cancelability type and state

are reset to PTHREAD_CANCEL_ENABLE and

PTHREAD_CANCEL_DEFERRED, respectively

Mutexes and

condition variables

No Yes See Section 33.3 for details of the treatment of

mutexes and other thread resources during

fork().

Priority and scheduling

Nice value Yes Yes nice(), setpriority().

Scheduling policy and priority Yes Yes sched_setscheduler(), sched_setparam().

Resources and CPU time

Resource limits Yes Yes setrlimit().

Process and child CPU times Yes No As returned by times().

Resource usages Yes No As returned by getrusage().

Interprocess communication

System V shared

memory segments

No Yes shmat(), shmdt().

POSIX shared memory No Yes shm_open() and related calls.

POSIX message queues No Yes mq_open() and related calls. Descriptors in child

and parent refer to same open message queue

descriptions. A child doesn’t inherit its parent’s

message notification registrations.

POSIX named semaphores No Shared sem_open() and related calls. Child shares

references to same semaphores as parent.

POSIX unnamed semaphores No See

notes

sem_init() and related calls. If semaphores are in

a shared memory region, then child shares

semaphores with parent; otherwise, child has its

own copy of the semaphores.

System V semaphore

adjustments

Yes No semop(). See Section 47.8.

File locks Yes See

notes

flock(). Child inherits a reference to the same

lock as parent.

Record locks See

notes

No fcntl(F_SETLK). Locks are preserved across exec()

unless a file descriptor referring to the file is

marked close-on-exec; see Section 55.3.5.

Table 28-4: Effect of exec() and fork() on process attributes (continued)

Process attribute exec() fork() Interfaces affecting attribute; additional notes